第1个回答 2010-02-28
分类讨论。(1)A={1,2,3}时,B应为{3,4,5,6}子集。有C(2,4)+C(3,4)+C(4,4)=6+4+1=11.(2)A={1,2,4}时,B应为{4,5,6}的子集。有C(2,3)+C(3,3)=3+1=4.(3)A={1,3,4}时,B应为{4,5,6}的子集。有4个。(4)A={1,2,5}时,B={5,6}.1个。(5)总之,A有10个,即(123),(124)(125)(134)(135)(145)(234)(235)(245)(345)。对应的B有11,4,1,4,1,4,1,1,1,1,其和=29.